This invention relates, in general, to stabilized aqueous enzyme compositions. More particularly, the invention relates to substantially unbuilt enzyme-containing liquid detergent compositions which provide improved enzyme stability in aqueous media and which contain saturated fatty acids and/or soaps as preferred components of the compositions.
The formulation of stable enzyme-containing liquid detergent compositions has been the focus of much attention in the prior art. The desirability of incorporating enzymes into detergent compositions is primarily due to the effectiveness of proteolytic and amylolytic enzymes in breaking down proteins and carbohydrates, thereby facilitating the removal of stains, such as gravy stains, egg stains, chocolate stains and the like, with water and detergent compounds. However, the instability of such enzymes in aqueous detergent compositions, as manifested by a rapid loss of enzyme activity during storage, is well known. Consequently, the use of enzymes in commercial liquid detergent compositions has heretofore been relatively limited.
Attempts to stabilize enzyme activity in aqueous media are extensively described in the patent literature. Among the approaches to the problem of enzyme stabilization has been the use of various organic materials, such as alcohols, polyols, esters and sugars which are said to have a stable effect upon enzymes. Water-soluble calcium salts have also been used to stabilize enzyme compositions. Thus, for example, U.S. Pat. No. 4,243,543 to Guilbert seeks to provide enzyme stability by adding an anti-oxidant and a polyol to aqueous detergent compositions, U.S. Pat. No. 4,111,855 to Barrat, et al. uses a combination of a polyacid and calcium ion as an enzyme stabilizer. U.S. Pat. No. 4,287,082 to Tolfo et al. discloses homogeneous enzyme-containing liquid detergents characterized by the presence of a saturated fatty acid, calcium ion and a specific short chain carboxylic acid. U.S. Pat. No. 4,318,818 to Letton et al. describes an enzyme composition which is stabilized by calcium ion and a short chain length carboxylic acid salt.